May 29, 2015 Get index of string in array at compile time | ||||
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I have define an immutable string array: [code] immutable string[] placeHolderDefinitionList = [ "<!-- fullname -->", "<!-- list item -->" ]; [/code] I need to get index of a string at compile time. So I have written a function as below: [code] public size_t getPlaceholderIndex(string PlaceHolderText)( size_t lookIndex = 0 ){ static if( lookIndex >= placeHolderDefinitionList.length ) return size_t.max; static if( placeHolderDefinitionList[lookIndex] == PlaceHolderText ) return lookIndex; else return getPlaceholderIndex( lookIndex + 1 ); } [/code] Called it as below: [code] writeln( "Index: ", getPlaceholderIndex!"<!-- list item -->"( 0 ) ); [/code] Compiler didn't like my code. It said those things to my face: main.d(22): Error: variable lookIndex cannot be read at compile time main.d(25): Error: variable lookIndex cannot be read at compile time main.d(28): Error: template main.getPlaceholderIndex cannot deduce function from argument types !()(ulong), candidates are: main.d(21): main.getPlaceholderIndex(string PlaceHolderText)(size_t lookIndex = 0) main.d(105): Error: template instance main.getPlaceholderIndex!"<!-- list item -->" error instantiating This is my first try with this type of code. So I am confused a little about what I should be doing. |
May 29, 2015 Re: Get index of string in array at compile time | ||||
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Posted in reply to tcak | On 05/29/2015 06:43 PM, tcak wrote: > I have define an immutable string array: > > [code] > immutable string[] placeHolderDefinitionList = [ > "<!-- fullname -->", > "<!-- list item -->" > ]; > [/code] > > I need to get index of a string at compile time. So I have written a > function as below: > > [code] > public size_t getPlaceholderIndex(string PlaceHolderText)( size_t > lookIndex = 0 ){ > static if( lookIndex >= placeHolderDefinitionList.length ) > return size_t.max; > > static if( placeHolderDefinitionList[lookIndex] == PlaceHolderText ) > return lookIndex; > else > return getPlaceholderIndex( lookIndex + 1 ); > } > [/code] > > Called it as below: > > [code] > writeln( "Index: ", getPlaceholderIndex!"<!-- list item -->"( 0 ) ); > [/code] > > Compiler didn't like my code. It said those things to my face: > > main.d(22): Error: variable lookIndex cannot be read at compile time > main.d(25): Error: variable lookIndex cannot be read at compile time > main.d(28): Error: template main.getPlaceholderIndex cannot deduce > function from argument types !()(ulong), candidates are: > main.d(21): main.getPlaceholderIndex(string > PlaceHolderText)(size_t lookIndex = 0) > main.d(105): Error: template instance main.getPlaceholderIndex!"<!-- > list item -->" error instantiating > > This is my first try with this type of code. So I am confused a little > about what I should be doing. The easiest way is to just write runtime code and evaluate it via CTFE: immutable string[] placeHolderDefinitionList = [ "<!-- fullname -->", "<!-- list item -->" ]; void main(){ import std.stdio, std.algorithm; enum index=placeHolderDefinitionList.countUntil("<!-- list item -->"); writeln("Index: ", index); } If you never need the placeHolderDefinitionList at runtime, make it enum instead of immutable. |
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