projects / OpenSPARC-T2-SAM / blame
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| 55 | <H2><A NAME="SECTION0021320000000000000000"> | |
| 56 | 19.3.2 Assignment nodes</A> | |
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| 58 | ||
| 59 | <P> | |
| 60 | There is a collection of nodes used to represent assignments. Each | |
| 61 | assignment statement in the source code becomes a single | |
| 62 | <tt class="class">Assign</tt> node in the AST. The <tt class="member">nodes</tt> attribute is a | |
| 63 | list that contains a node for each assignment target. This is | |
| 64 | necessary because assignment can be chained, e.g. <code>a = b = 2</code>. | |
| 65 | Each <tt class="class">Node</tt> in the list will be one of the following classes: | |
| 66 | <tt class="class">AssAttr</tt>, <tt class="class">AssList</tt>, <tt class="class">AssName</tt>, or | |
| 67 | <tt class="class">AssTuple</tt>. | |
| 68 | ||
| 69 | <P> | |
| 70 | Each target assignment node will describe the kind of object being | |
| 71 | assigned to: <tt class="class">AssName</tt> for a simple name, e.g. <code>a = 1</code>. | |
| 72 | <tt class="class">AssAttr</tt> for an attribute assigned, e.g. <code>a.x = 1</code>. | |
| 73 | <tt class="class">AssList</tt> and <tt class="class">AssTuple</tt> for list and tuple expansion | |
| 74 | respectively, e.g. <code>a, b, c = a_tuple</code>. | |
| 75 | ||
| 76 | <P> | |
| 77 | The target assignment nodes also have a <tt class="member">flags</tt> attribute that | |
| 78 | indicates whether the node is being used for assignment or in a delete | |
| 79 | statement. The <tt class="class">AssName</tt> is also used to represent a delete | |
| 80 | statement, e.g. <tt class="class">del x</tt>. | |
| 81 | ||
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| 83 | When an expression contains several attribute references, an | |
| 84 | assignment or delete statement will contain only one <tt class="class">AssAttr</tt> | |
| 85 | node - for the final attribute reference. The other attribute | |
| 86 | references will be represented as <tt class="class">Getattr</tt> nodes in the | |
| 87 | <tt class="member">expr</tt> attribute of the <tt class="class">AssAttr</tt> instance. | |
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