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digitalmars.D.learn - correct way to create boiler plate code

reply dmerrio <rdmerrio gmail.com> writes:
I am parsing some formulas from a spreadsheet file. To duplicate
the behavior of the spreadsheet functions, I am having to create a
lot of boiler plate code that maps from the spreadsheet functions
to the built-in functions. Mixin would seem to allow me to
automate the boiler-plate creation, but i am not utilizing it
correctly. What is the correct to call Mixin in this situation, or
is their a better way to create the boiler-plate code?

For background, i am new to D. D is my second language with my
primary experience being a script kiddie in Excel VBA, so take it
slow, please.



import main; //class definition of rng
import std.math; //trig functions
import std.conv; //to!double
import std.string; //toupper

double transFunc(alias transedentalFunc)(rng aRng){
	try{return(transedentalFunc(aRng.getCellValue().coerce!
(double)));} //cellValue stored as a Variant
	catch{return(transedentalFunc(to!double(aRng.getCellValue
().coerce!(string))));} //replicate spreadsheet behavior and
convert to a number
}

//Example 1 of boilerplate code
double SIN(double aReal){return(sin(aReal));}
double SIN(string aStr){return(sin(to!double(aStr)));}
double SIN(rng aRng){return(transFunc!(sin)(aRng));}

//Example 2 of boilerplate code
double COS(double aReal){return(cos(aReal));}
double COS(string aStr){return(cos(to!double(aStr)));}
double COS(rng aRng){return(transFunc!(cos)(aRng));}

string[] funcs = ["tan"];
void createFuncs(){
	foreach(func; funcs){
		mixin("double " ~ toupper(func) ~ "(double aReal)
{return(" ~ func ~ "(aReal));}");
	}
}

calling mixin a compile time has the following error...

Error	1	Error: variable func cannot be read at compile time
	C:\D\SVNProjects\trunk\xcellD\xcell1\trig.d	22


thanks for your help
May 16 2011
next sibling parent reply Trass3r <un known.com> writes:
 string[] funcs = ["tan"];



 calling mixin a compile time has the following error...

 Error	1	Error: variable func cannot be read at compile time
 	C:\D\SVNProjects\trunk\xcellD\xcell1\trig.d	22


That's because funcs is mutable.
Try to make it immutable or enum.
May 16 2011
parent dmerrio <rdmerrio gmail.com> writes:
changing the relevent code, changes the error, but it still does
not compile...

immutable funcs = ["tan"];
void createFuncs(){
	foreach(func; funcs){
		mixin("double " ~ toupper(func) ~ "(double aReal)
{return(" ~ func ~ "(aReal));}");
	}
}

new error...
Error	1	Error: argument to mixin must be a string, not
("double TAN(double aReal){return(" ~ func ~ "(aReal));}")
	C:\D\SVNProjects\trunk\xcellD\xcell1\trig.d	24


Thanks for the suggestion, any others????
May 16 2011
prev sibling next sibling parent reply Timon Gehr <timon.gehr gmx.ch> writes:
 I am parsing some formulas from a spreadsheet file. To duplicate
 the behavior of the spreadsheet functions, I am having to create a
 lot of boiler plate code that maps from the spreadsheet functions
 to the built-in functions. Mixin would seem to allow me to
 automate the boiler-plate creation, but i am not utilizing it
 correctly. What is the correct to call Mixin in this situation, or
 is their a better way to create the boiler-plate code?

 For background, i am new to D. D is my second language with my
 primary experience being a script kiddie in Excel VBA, so take it
 slow, please.


hi,

Disregard the other answer, making func immutable won't solve your problem.


 string[] funcs = ["tan"];
 void createFuncs(){
  foreach(func; funcs){
   mixin("double " ~ toupper(func) ~ "(double aReal)
 {return(" ~ func ~ "(aReal));}");
  }
 }



foreach runs at runtime, while mixin is expanded at compile time.

If you want to inject your boilerplate into module namespace, you would rather
write a function that generates the code and mixin the result of a call to that
function:

string[] funcs = ["tan"];
string createFuncs(){
  string res;
  foreach(func; funcs){
    res~="double " ~ toupper(func) ~ "(double aReal){return(" ~ func ~
"(aReal));}";
  }
  return res;
}
mixin(createFuncs());
May 16 2011
parent Trass3r <un known.com> writes:
 foreach runs at runtime, while mixin is expanded at compile time.


Not the whole truth though.

foreach over tuples gets unrolled at compile time so you can do stuff like:

// +=, -=, ...
Vector opOpAssign(string op, U)(U s)
{
	foreach (i, _; tuple)
		mixin("tuple[i] " ~ op ~ "= s;");
	return this;
}
May 16 2011
prev sibling next sibling parent reply Kai Meyer <kai unixlords.com> writes:
On 05/16/2011 01:08 PM, dmerrio wrote:

 I am parsing some formulas from a spreadsheet file. To duplicate
 the behavior of the spreadsheet functions, I am having to create a
 lot of boiler plate code that maps from the spreadsheet functions
 to the built-in functions. Mixin would seem to allow me to
 automate the boiler-plate creation, but i am not utilizing it
 correctly. What is the correct to call Mixin in this situation, or
 is their a better way to create the boiler-plate code?

 For background, i am new to D. D is my second language with my
 primary experience being a script kiddie in Excel VBA, so take it
 slow, please.



 import main; //class definition of rng
 import std.math; //trig functions
 import std.conv; //to!double
 import std.string; //toupper

 double transFunc(alias transedentalFunc)(rng aRng){
 	try{return(transedentalFunc(aRng.getCellValue().coerce!
 (double)));} //cellValue stored as a Variant
 	catch{return(transedentalFunc(to!double(aRng.getCellValue
 ().coerce!(string))));} //replicate spreadsheet behavior and
 convert to a number
 }

 //Example 1 of boilerplate code
 double SIN(double aReal){return(sin(aReal));}
 double SIN(string aStr){return(sin(to!double(aStr)));}
 double SIN(rng aRng){return(transFunc!(sin)(aRng));}

 //Example 2 of boilerplate code
 double COS(double aReal){return(cos(aReal));}
 double COS(string aStr){return(cos(to!double(aStr)));}
 double COS(rng aRng){return(transFunc!(cos)(aRng));}

 string[] funcs = ["tan"];
 void createFuncs(){
 	foreach(func; funcs){
 		mixin("double " ~ toupper(func) ~ "(double aReal)
 {return(" ~ func ~ "(aReal));}");
 	}
 }

 calling mixin a compile time has the following error...

 Error	1	Error: variable func cannot be read at compile time
 	C:\D\SVNProjects\trunk\xcellD\xcell1\trig.d	22


 thanks for your help


This works:

//import main; //class definition of rng
import std.math; //trig functions
import std.conv; //to!double
import std.string; //toupper
import std.stdio;

void main()
{
     mixin(createFunc!("sin"));
     mixin(createFunc!("cos"));
     mixin(createFunc!("tan"));
     writeln(SIN(0)); // 0
     writeln(COS(0)); // 1
     writeln(TAN(0)); // 0
     return;
}
template createFunc(string func){
     const char[] createFunc = "double " ~ toupper(func) ~ "(double aReal)
         {return(" ~ func ~ "(aReal));}";
}

Stole it from http://www.digitalmars.com/d/2.0/mixin.html

I don't think there's a way to use an array of strings, since (as 
pointed out by others and your error message) that mixins are done 
compile-time and foreach are done (mostly) at run-time.
May 16 2011
parent dmerrio <rdmerrio gmail.com> writes:
Thank you for the reply. Potential, but there still seems to be
alot of repetitive code.
May 16 2011
prev sibling parent reply bearophile <bearophileHUGS lycos.com> writes:
dmerrio:


 import main; //class definition of rng
 import std.math; //trig functions
 import std.conv; //to!double
 import std.string; //toupper
 
 double transFunc(alias transedentalFunc)(rng aRng){
 	try{return(transedentalFunc(aRng.getCellValue().coerce!
 (double)));} //cellValue stored as a Variant
 	catch{return(transedentalFunc(to!double(aRng.getCellValue
 ().coerce!(string))));} //replicate spreadsheet behavior and
 convert to a number
 }
 
 //Example 1 of boilerplate code
 double SIN(double aReal){return(sin(aReal));}
 double SIN(string aStr){return(sin(to!double(aStr)));}
 double SIN(rng aRng){return(transFunc!(sin)(aRng));}


Mine is not an answer that directly helps you solve your problem. Experience
shows that messy code doesn't help you see your problems, and sometimes it even
hides bugs. So I suggest you to reformat your code in a more human way, use
more normal naming conventions, and use named imports if you want to import
just some names.

This means writing:
import std.conv: to;
Instead of:
import std.conv; //to!double

To put a newline before the closing brace, to add spaces and newlines where
they are belong, and so on. This helps a lot.

Bye,
bearophile
May 16 2011
parent dmerrio <rdmerrio gmail.com> writes:
Thanks for the formatting tips. Copy and pasting kind of messed up
the formatting, not that it was good to start with. I am still
developing a coding style.

== Quote from bearophile (bearophileHUGS lycos.com)'s article

 dmerrio:

 import main; //class definition of rng
 import std.math; //trig functions
 import std.conv; //to!double
 import std.string; //toupper

 double transFunc(alias transedentalFunc)(rng aRng){
 	try{return(transedentalFunc(aRng.getCellValue().coerce!
 (double)));} //cellValue stored as a Variant
 	catch{return(transedentalFunc(to!double(aRng.getCellValue
 ().coerce!(string))));} //replicate spreadsheet behavior and
 convert to a number
 }

 //Example 1 of boilerplate code
 double SIN(double aReal){return(sin(aReal));}
 double SIN(string aStr){return(sin(to!double(aStr)));}
 double SIN(rng aRng){return(transFunc!(sin)(aRng));}


 Mine is not an answer that directly helps you solve your


problem. Experience shows that messy code doesn't help you see
your problems, and sometimes it even hides bugs. So I suggest you
to reformat your code in a more human way, use more normal naming
conventions, and use named imports if you want to import just some
names.

 This means writing:
 import std.conv: to;
 Instead of:
 import std.conv; //to!double
 To put a newline before the closing brace, to add spaces and


newlines where they are belong, and so on. This helps a lot.

 Bye,
 bearophile
May 16 2011