Interacting with Files and Generating Code in Maple for Symbolic Computation - Prof. Jan V, Study notes of Computer Science

Download Interacting with Files and Generating Code in Maple for Symbolic Computation - Prof. Jan V and more Study notes Computer Science in PDF only on Docsity! MCS 320 Introduction to Symbolic Computation Spring 2003 9. Import/export of data; Low-Level I/O; Code generation In this lecture we go deeper into the capabilities of Maple to interact at a low level to retrieve or save data. We end this part with a demonstration how Maple can generate code. 9.1 Import/export of data Raw numerical data in the form of matrices of floating-point numbers can be brought in and out of Maple with the commands readdata and writedata. Let us first create a matrix: [> indfun := (i,j) -> 1/(i+j-1); # index function [> data := matrix(3,5,indfun); # 3-by-5 Hilbert matrix [> Digits := 20: # write a 20 digit approximation to file [> writedata(terminal,data,float); # first write to terminal as test [> writedata("C:\\MCS320\\mydata",data,float); [> data := ’data’; # release variable to check retrieval Matrices in readdata are considered to be organized columnwise. Besides the file, we give in the number of columns we wish to read : [> data := readdata("C:\\MCS320\\mydata",5); 9.2 Low-Level I/O We can manipulate files very much like if we were programming in C. A sample session is below: [> ourfile := "C:\\MCS320\\testfile": [> fopen(ourfile,WRITE,TEXT); [> n := writeline(ourfile,‘this is some text‘); [> fclose(ourfile); [> fopen(ourfile,READ,TEXT); [> readline(ourfile); [> fclose(ourfile); [> fopen(ourfile,APPEND,TEXT); [> fprintf(ourfile,"number of characters on previous line :%d\n",n); [> fclose(ourfile); 9.3 Code Generation If we wish to export functions, for example to evaluate polynomials or other mathematical expressions, we can generate C or Fortran code. [> with(codegen); [> p := x^4 + 3*x + 2; [> fortran(p,’optimized’,precision=double,mode=double); [> C(p); Jan Verschelde, February 3, 2003 UIC, Dept of Math, Stat & CS Lecture 9, page 1