Beginning Programming (Pascal) Lecture 75. Figure 1. type-declarations. simple-type. pointer-type. array-type. file-type. set-type.

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1 -declarations -identifier = ; ; Figure 1. -declarations simple- pointer- array- file- set- record- Figure 2. simple- standard- subrange- enumerated- Figure 3. simple- standard- boolean char integer real Figure 4. standard- 1

2 enumerated- ( ) enumerataion-constant-identifier Figure 5. enumerated- Definition: An enumerated- defines the values of the as an ordered set of constant identifiers. Each identifier in the set is a name for a whole number. For example: color_t=(red,white,blue);, Type identifier color_t is the name of the. Enumeration constants, red, white, and blue are the values that a variable of color_t can take on. Enumeration constants red, white, and blue have ordinal values of zero, one and two respectively. 1 program p01; 7 begin{p01} 8 season:=autumn; 9 writeln('season=',ord(season)) 10 end{p01}. Figure 6. Program p01 Figure 7. Output for program p01 Program p01 notes: 1. Variable season can take on any one of the set of values defined by season_t. 2. On line 8, the enumeration constant autumn is assigned to variable season. 3. On line 9, the ordinal value of variable season is displayed. Standard procedure writeln cannot format variable season since season_t is a user-defined. 2

3 1 program p02; 7 begin{p02} 8 for season:=spring to winter do 9 writeln('season=',ord(season)) 10 end{p02}. Figure 8. Program p02 season=0 season=1 season=3 Figure 9. Output for program p02 Program p02 notes: 1. Type season_t defines a sequence. The sequence is spring, summer, autumn, and winter. The sequence makes sense to us for we recognize the order of the seasons. The sequence makes sense to Pascal in that the order we recognize is preserved in the ordinal values of the. 1 program p03; 7 begin{p03} 8 season:=spring; 9 while season <= autumn do 10 begin 11 writeln('season=',ord(season)); 12 season:=succ(season) 13 end{while} 14 end{p03}. Figure 10. Program p03 season=0 season=1 Figure 11. Output for program p03 3

4 Program p03 notes: 1. Program p03 illustrates the use of standard function succ. Standard function succ is used to increment the loop-variable season. 2. The while-statement in program p03 approximates the for-statement in program p The terminal value, winter, used in the for-statement cannot be used in the while-statement. In order for the while-statement to terminate, the expression in the while-statement must evaluate to false. The expression cannot be false until the ordinal value of season is equal five (5). Type season_t has no value whose ordinal value is equal to five (5). 1 program p04; 7 a:integer; 8 function seasonsucc(s:season_t):season_t; 9 begin{seasonsucc} 10 if s=winter then 11 seasonsucc:=spring 12 else 13 seasonsucc:=succ(s) 14 end{seasonsucc}; 15 begin{p04} 16 season:=spring; 17 writeln('a':4,' season'); 18 for a:=1 to 8 do 19 begin 20 writeln(a:4,ord(season):7); 21 season:=seasonsucc(season) 22 end{for} 23 end{p04}. Figure 12. Program p04 a season Figure 13. Output for program p04 Program p04 notes: 1. Program p04 illustrates the concept of successor amplified for repeating sequences. Spring follows winter but the ordinal value zero (0) does not logically follow three (3). Function seasonsucc makes spring follow winter. 4

5 1 program p05; 7 a:integer; 8 function seasonsucc(s:season_t):season_t; 9 begin{seasonsucc} 10 if s=winter then 11 seasonsucc:=spring 12 else 13 seasonsucc:=succ(s) 14 end{seasonsucc}; 15 procedure seasonwrite(s:season_t; var f:text); 16 begin{seasonwrite} 17 case s of 18 spring: write(f,'spring'); 19 summer: write(f,'summer'); 20 autumn: write(f,'autumn'); 21 winter: write(f,'winter') 22 end{case s} 23 end{seasonwrite}; 24 begin{p05} 25 season:=spring; 26 writeln('a':4,' season'); 27 for a:=1 to 8 do 28 begin 29 write(a:4); 30 write(' '); 31 seasonwrite(season,output); 32 writeln; 33 season:=seasonsucc(season) 34 end{for} 35 end{p05}. Figure 14. Program p05 a season 1 spring 2 summer 3 autumn 4 winter 5 spring 6 summer 7 autumn 8 winter Figure 16. Output for program p05 Program p05 notes: 1. Program p05 shows how to print the enumeration-constant-identifier. Function seasonwrite uses a case-statement to write the appropriate identifier. 2. Enumeration s and case-statements are often used in conjunction. 5