/disk1/scratch/aselle/projects/seexpr/SeExpr/src/demos/asciiGraph.cpp

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/*
* (c) Disney Enterprises, Inc.  All rights reserved.
*
* This file is licensed under the terms of the Microsoft Public License (MS-PL)
* as defined at: http://opensource.org/licenses/MS-PL.
*
* A complete copy of this license is included in this distribution as the file
* LICENSE.
*/
#include <SeExpression.h>
#include <cstdlib>
#include <cstdio>
#include <cstring>

class GrapherExpr:public SeExpression
{
public:
    GrapherExpr(const std::string& expr)
        :SeExpression(expr)
    {}

    void setX(double x_input)
    {x.val=x_input;}

private:
    struct SimpleVar:public SeExprScalarVarRef
    {
        double val; // independent variable
        void eval(const SeExprVarNode* /*node*/,SeVec3d& result)
        {result[0]=val;}
    };
    
    mutable SimpleVar x;

    SeExprVarRef* resolveVar(const std::string& name) const
    {
        if(name == "x") return &x;
        return 0;
    }
};



int main(int argc,char *argv[])
{
    std::string exprStr="\
                         $val=.5*PI*x;\
                         7*sin(val)/val \
                         ";
    if(argc == 2){
        exprStr=argv[1];
    }
    GrapherExpr expr(exprStr);

    if(!expr.isValid()){
        std::cerr<<"expression failed "<<expr.parseError()<<std::endl;
        exit(1);
    }
    double xmin=-10,xmax=10,ymin=-10,ymax=10;
    int w=60,h=30;
    char *buffer=new char[w*h];
    memset(buffer,(int)' ',w*h);

    // draw x axis
    int j_zero=(-ymin)/(ymax-ymin)*h;
    if(j_zero>=0 && j_zero<h){
        for(int i=0;i<w;i++){
            buffer[i+j_zero*w]='-';
        }
    }
    // draw y axis
    int i_zero=(-xmin)/(xmax-xmin)*w;
    if(i_zero>=0 && i_zero<w){
        for(int j=0;j<h;j++){
            buffer[i_zero+j*w]='|';
        }
    }

    // evaluate the graph
    const int samplesPerPixel=10;
    const double one_over_samples_per_pixel=1./samplesPerPixel;
    for(int i=0;i<w;i++){
        for(int sample=0;sample<samplesPerPixel;sample++){
            // transform from device to logical coordinatex
            double dx=double(sample)*one_over_samples_per_pixel;
            double x=double(dx+i)/double(w)*(xmax-xmin)+xmin;
            // prep the expression engine for evaluation
            expr.setX(x);
            // evaluate and pull scalar value
            SeVec3d val=expr.evaluate();
            double y=val[0];
            // transform from logical to device coordinate
            int j=(y-ymin)/(ymax-ymin)*h;
            // store to the buffer
            if(j>=0 && j<h)
                buffer[i+j*w]='#';
        }
    }

    // draw the graph from the buffer
    for(int j=h-1;j>=0;j--){
        for(int i=0;i<w;i++){
            std::cout<<buffer[i+j*w];
        }
        std::cout<<std::endl;
    }

    return 0;
}

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