Workshop: Towards Highly Portable Software Jakarta, 20 – 23 January 2003 Diselenggarakan oleh Universitas IndonesiaUniversitas Indonesia Using Pretty Printing Combinator Dr. Ir. I.S.W.B. A. Azurat

2 Pretty Printing Library How to pretty print some output nicely based on some layout → use lay out combinator (use UU_Pretty Library) Run hugs with option : hugs -98 +o –P:”c:\tools\UU.lib” height width last line

3 PP Document The basic building blocks for pretty-printing are PP documents (of type PP_Doc ). You obtain PP documents either by : 1.using the primitive text 2.combining PP documents with the pretty-printing operators.

4 Basic interface InterfaceComments empty The empty PP document and null element for the operations beside and above text s Converts the string s into a PP document render ppd pw Prints the PP document ppd (to IO () ) in a page pw (>=0) wide

5 example We are ready to try out the first examples: > tenplus = " ha!" > t_text = render (text tenplus) 15 whose output is ha!. But: > t_error = render (text tenplus) 10 will result in, because the page is not wide enough. The number of characters of the output line is the actual width of the input string.

6 Basic Combinator x >|< y x beside y x >-< y x above y

7 example Horizontal (beside) and vertical (above) composition are the principal combinators used to build more complex documents. For example: > hello = "hello" > world = "world!" > h_beside_w = hello >|< world > t_beside = render h_beside_w 20 (Hint: Try to use ># |<, what is the difference ? )

8 Exercise Run hugs with option : -98 +o –P:”c:\tools\UU.lib”

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