Smalltalk Smalltalk
3/8/2008 CSE 3302 Programming Languages Smalltalk Everyygthing is obj ect. Obj ects communicate by messages. Chengkai Li Spring 2008 Lecture 14 – Smalltalk, Spring Lecture 14 – Smalltalk, Spring CSE3302 Programming Languages, UT-Arlington 1 CSE3302 Programming Languages, UT-Arlington 2 2008 ©Chengkai Li, 2008 2008 ©Chengkai Li, 2008 Object Hierarchy Object UndefinedObject Boolean Magnitude Collection No Data Type. True False Set … There is only Class. Char Number … Fraction Integer Float Lecture 14 – Smalltalk, Spring Lecture 14 – Smalltalk, Spring CSE3302 Programming Languages, UT-Arlington 3 CSE3302 Programming Languages, UT-Arlington 4 2008 ©Chengkai Li, 2008 2008 ©Chengkai Li, 2008 Syntax • Smalltalk is really “small” – Only 6 keywords (pseudo variables) – Class, object, variable, method names are self explanatory Sma llta lk Syn tax is Simp le. – Only syntax for calling method (messages) and defining method. • No syntax for control structure • No syntax for creating class Lecture 14 – Smalltalk, Spring Lecture 14 – Smalltalk, Spring CSE3302 Programming Languages, UT-Arlington 5 CSE3302 Programming Languages, UT-Arlington 6 2008 ©Chengkai Li, 2008 2008 ©Chengkai Li, 2008 1 3/8/2008 Expressions Literals • Literals • Number: 3 3.5 • Character: $a • Pseudo Variables • String: ‘ ’ (‘Hel’,’lo!’ and ‘Hello!’ are two objects) • Symbol: # (#foo and #foo are the same object) • Variables • Compile-time (literal) array: #(1 $a 1+2) • Assignments • Run-time (dynamic) array: {1. $a. 1+2} • Comment: “This is a comment.” • Blocks • Messages Lecture 14 – Smalltalk, Spring Lecture 14 – Smalltalk, Spring CSE3302 Programming Languages, UT-Arlington 7 CSE3302 Programming Languages, UT-Arlington 8 2008 ©Chengkai Li, 2008 2008 ©Chengkai Li, 2008 Pseudo Variables Variables • Instance variables.
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