00100	
00200	
00300	
00400	
00500	
00600	
00700	
00800	
00900	
01000	
01100	
01200	
01300	
01400	SOME DIFFERENCES BETWEEN SAIL AND ALGOL-60
01500	
01600	Larry Tesler
01700	September 1972
01800	
01900	
02000	
02100	
02200	
02300	
02400	
02500	
02600	
02700	
02800	This is intended to introduce new users of SAIL to the system if
02900	they are already familiar with Algol-60.  At first, the user shoulld
03000	be able to produce small programs with occasional reference to the
03100	SAIL Manual proper.  Eventually, it is recommended that the entire
03200	SAIL Manual be read.
     

00100	                             IDENTIFIERS
00200	
00300	Capital and small letters are not distinguished.  These are all the
00400	same to SAIL:
00500	
00600		alpha
00700		Alpha
00800		ALPHA
00900	
01000	Although the length of an identifier is unlimited, it is recommended
01100	that it be distinguishable by its first six characters.  [Only the
01200	first six characters are available in the run-time symbol table used
01300	by RAID (DDT).  Problems also arise when a large program is broken up
01400	into separately compiled modules, and when an assembly language
01500	program is loaded with a SAIL program.]
01600	
01700	
01800	                             PROCEDURES
01900	
02000	Types of formal parameters are specified within the parentheses of
02100	the procedure declaration, along with the names of the parameters.
02200	
02300		PROCEDURE P(INTEGER A, B; STRING S) ;
02400	
02500	Numbers and strings are passed by value and arrays by location.  To
02600	pass a simple variable by location, use the qualifier REFERENCE in
02700	the procedure declaration.
02800	
02900		PROCEDURE Q(REFERENCE INTEGER I; INTEGER ARRAY P) ;
03000			P[I] ← I ← 4*I + 1 ;
03100	
03200	There is no Algol-call-by-name; i.e., if an expression is an actual
03300	parameter, it is evaluated only once, at the time of the call.
03400	
03500	A recursive procedure must be declared as such.  A typed procedure
03600	must have a RETURN statement somewhere in its body.
03700	
03800		RECURSIVE INTEGER PROCEDURE FACTORIAL(INTEGER N) ;
03900			RETURN(IF N=0 THEN 1 ELSE N * FACTORIAL(N-1)) ;
04000	
04100	
04200	                        ARITHMETIC OPERATORS
04300	
04400	Multiplication *
04500	
04600	Division / %	The latter is integer division INT%INT→INT
04700	
04800	Modulus MOD	Uses infix notation: A MOD B
04900	
     

00100	                              CONSTANTS
00200	
00300	Real	6.4@-7 = .00000064
00400	
00500	Integer	-14
00600	
00700	String	"This is how to get a "" into a string"
00800	
00900	Octal Integer '7677
01000	
01100	
01200	                          STRING OPERATORS
01300	
01400	Automatic conversion of small octal character code to string value
01500	
01600		CR ← '15 ; LF ← '12 ;
01700	
01800	Concatenation
01900	
02000		B ← "Long " & "message." & CR ;
02100	
02200	Function CVS to convert integer to string for output
02300	
02400		STR ← CVS(14-J)
02500	
02600	Function OUTSTR to output a string to the terminal
02700	
02800		OUTSTR("This is a " & B & LF & " X = " & CVS(X) & CR & LF) ;
02900	
03000	Equality of strings
03100	
03200		IF EQU(STR, "D<<@.") THEN ...
03300	
03400	Length of a string
03500	
03600		L ← LENGTH(STR)
03700	
03800	Substring
03900	
04000		STR[4 TO 7]
04100		B[∞-6 TO ∞]	...∞ means last character
04200	
04300	                              ITERATION
04400	
04500		FOR I ← A+B STEP C-1 UNTIL Q*R DO ...
04600	
04700	In the above, A+B and C-1 are evaluated just once each, but Q*R is
04800	evaluated each time through the loop.  But if the STEP expression is
04900	a simple variable, it is re-evaluated every time too.
05000	
05100		WHILE A<0 OR B>0 DO ...
05200	
05300		DO ...  UNTIL (BOOL ∨ ¬LOOB) ∧ Q>Y≥0
     

00100	           OTHER FEATURES OF SAIL (SEE MANUAL FOR DETAILS)
00200	
00300	
00400		The `*' marks facilities recently added to SAIL and not yet
00500		in the manual.  See SAIL.NEW[UP,DOC]
00600	
00700	 CASE Statements and Expressions
00800	
00900	*SIMPLE PROCEDURES	Extra efficiency, a few restrictions
01000	
01100	 SCAN, INPUT		String scanning, file input
01200	
01300	 LEAP			Powerful associative processor, set and list
01400				operations
01500	
01600	*Multiple processes
01700	
01800	*Macros and Conditional Assembly