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EZGraphs. Vincent Dobrev vd2006@columbia.edu Edlira Kumbarce ek2248@columbia.edu. A graphs and charts generating language. COMS W4115: Programming Languages and Translators Spring 2007. Introduction. Why graphs?
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EZGraphs Vincent Dobrev vd2006@columbia.edu Edlira Kumbarce ek2248@columbia.edu A graphs and charts generating language COMS W4115: Programming Languages and Translators Spring 2007
Introduction • Why graphs? Graphs are used widely. They communicate information more easily and efficiently than words or tables. • Objective Provide a language that can be used to create charts and graphs, targeting those with a little prior programming experience.
Features • User-Friendly Syntax Very similar to C and Java. Intuitive keywords and internal function names. More organized than Ploticus. • Easy Debugging Non-cryptic and informative error messages make it easy to use and debug. User given exact location of error with file name and line and column numbers.
Features (cont’d) • Portability Based on Java, so it only depends on the presence of the Java Runtime Environment. • Data Types & Operators Supports boolean, integer, floating-point, and string data types, as well as multi-dimensional arrays.
Features(cont’d) • File Inclusion Allows code reuse and modularity. More organized programs. • Control Flow Statements Supports conditionals (if-then-else) and iterative statements (loops), which in turn enable user to create recursive functions.
Features(cont’d) • Pre-Defined Functions • Drawing: point(), line(), polygon(), etc. • Transfromation: translate(), scale(), shear() etc. • Data Acquiring: data() • Math: exp(), log(), pow(), sqrt(), etc. • Auxiliary: strToInt(), strToFloat(), substring(), size(), etc. • Output: print(), println() , save(), show()
Example 1 - Recursion /* * Sierpinski Triangle. */ void main() { canvas(600, 600); scale(1, -1); translate(0, -600); triangles(50, 50, 550, 50, 300, 550, 1); show(); } void triangles(int x1, int y1, int x2, int y2, int x3, int y3, int level) { line(x1, y1, x2, y2); line(x2, y2, x3, y3); line(x3, y3, x1, y1); int xp1 = (x2+x1) / 2; int yp1 = (y2+y1) / 2; int xp2 = (x3+x2) / 2; int yp2 = (y3+y2) / 2; int xp3 = (x1+x3) / 2; int yp3 = (y1+y3) / 2; if (level < 8) { triangles(x1, y1, xp1, yp1, xp3, yp3, level+1); triangles(xp1, yp1, x2, y2, xp2, yp2, level+1); triangles(xp3, yp3, xp2, yp2, x3, y3, level+1); } }
Example 2 - A Pie Chart /* * A pie chart illustrating distribution of income. */ void main() { int fields = 7; /* Colors. */ int[][] c = new int[fields][3]; c[0][0] = 255; c[0][1] = 50; c[0][2] = 0; c[1][0] = 0; c[1][1] = 255; c[1][2] = 0; ... c[6][0] = 255; c[6][1] = 255; c[6][2] = 0; /* Labels. */ string[] l = new string[fields]; l[0] = "Savings"; l[1] = "Insurance"; ... l[6] = "Housing"; /* Percentages. */ int[] p = new int[fields]; p[0] = 9; p[1] = 11; ... p[6] = 21; ...
Example 2 - A Pie Chart (cont’d) canvas(400,400); background(244,244,244); string title = "Income Distribution"; font("Arial", 0, 20); int width = width(title); text(title, 200 - width/2, 40); stroke(2); line(50,50,350,50); translate(100,100); int start = 0, end = 0; for (int i = 0; i < fields; i++) { color(c[i][0],c[i][1],c[i][2]); start += end; end = p[i] * 360 / 100; fillArc(0,0,200,200,start,end); } show(); } Output:
Language Implementation • The source code is parsed and executed right away with no intermediate code. • Programs reside in .ezg files, with one file containing a main() function and any number of other .ezg files containing other functions.
Language Implementation (cont’d) • Three types of output: • Text in the console • An image in a window on-screen • An image in a file • Exception handling mechanism catches, formats, • and prints out error messages for the user. • Examples: • Error: draw.ezg:48:10: expecting ID, found '=‘ • Error: draw.ezg:59:6: unexpected data type being assigned to array • Error: recursion.ezg:5:5: function fact(int) expected to return int • Error: recursion.ezg:7:16: variable g not declared
