*To*: mathgroup@smc.vnet.net*Subject*: [mg11177] Re: Mathlink problem with lists of reals*From*: kevinl@wolfram.com (Kevin Leuthold)*Date*: Wed, 25 Feb 1998 03:31:48 -0500*Organization*: Wolfram Research, Inc.*References*: <6ctk8a$lvb@smc.vnet.net>

Dave, The reason WriteSample is returning is because of what you have in your :Pattern: field in your template file. The :Pattern: field specifies the pattern matching that your Mathematica function will do, and the patterns here should match the Heads of the expressions your function expects. So you should change your :Pattern: field to: :Pattern: WriteSample[filename_String, ns_List] (See the Mathematica Book (Third Edition), section 2.12.4 for an example of sending a List to a template-based MathLink program). Also, to see what patterns are defined for your installed program, you can use the LinkPatterns function. Kevin Leuthold MathLink Group Wolfram Research Dave Grosvenor <dag@hplb.hpl.hp.com> writes: >Briefly >-------- >Has anyone else had a problem passing a list of Reals from mathematica >to a c program? >Or am I making a real simple mistake? >I would be grateful for examples which do something similar. >Thanks > Dave Grosvenor >In detail >---------- >I have got mathlink to pass lists of reals from c to mathematica. But >now I want to write the reals to a specified file. This is so simple >I cannot beleive it is not working. >I define the following template >:Begin: >:Function: writesample >:Pattern: WriteSample[filename_String, ns_RealList] >:Arguments: {filename, ns} >:ArgumentTypes: {String, RealList} >:ReturnType: Integer >:End: >This is called as follows:- >WriteSample["test.txt",{1.1,2.2}] >evaluating to >WriteSample["test.txt",{1.1,2.2}] >The call never reaches my c function code, which is defined as follows:- >int main(int argc,char* argv[]) >{ >int result; >result = MLMain(argc,argv); >return result; >} >int writesample(char* filename,double px[],long nx) { >FILE* outp = fopen(filename,"wb"); >long i; >for (i=0;i<nx;i++){ > fprintf(outp,"%e\n",px[i]); >} >fclose(outp); >} >I have put in assert(1!=1) at various points in the writesampletm.c file >which was generated from the template, and it seems to fail much >earlier...